Conventionally, projection type display apparatuses using various types of spatial light modulators have been known as video equipment for use with a large screen. Such a projection type display apparatus uses, for example, a transmission type or reflection type liquid crystal panel as a spatial light modulator and has a configuration in which the liquid crystal panel is illuminated by a light source, and an optical image according to an externally supplied video signal is formed on the liquid crystal panel and is projected in a magnified state on a screen by a projection lens.
In recent years, with the need for higher luminance growing, a projection type display apparatus of a three-panel system that uses three spatial light modulators such as liquid crystal panels has become mainstream. However, such a projection type display apparatus has presented a problem of an increase in overall cost of the apparatus.
Meanwhile, a projection type display apparatus of a single-panel system has been known that uses only one liquid crystal panel so that a cost reduction is achieved. However, such a projection type display apparatus has presented a problem that color filters of three primary colors need to be provided in each pixel on a liquid crystal panel, resulting in a substantial deterioration in resolution. Further, such a display apparatus has presented another problem in that about two-thirds of illumination light is lost at the color filters, resulting in a deterioration in luminance of a screen.
With respect to the above-described problems, a projection type display apparatus of a color sequential system has been known that uses a disk-shaped color wheel (see, for example, Patent Document 1). According to this system, a single spatial light modulator is irradiated sequentially with lights of three primary colors of red, green and blue, and thus a full-color display is performed.
FIG. 9 is a structural view showing an example of a configuration of such a projection type display apparatus. In FIG. 9, white light radiated from a light-emitting portion of a discharge lamp 100, which is formed of a pair of electrodes 100a, is condensed by a concave mirror 101 onto a color wheel 103 via a UV-IR cut-off filter 102. The UV-IR cut-off filter 102 is used to remove ultraviolet rays and infrared rays from light radiated from the discharge lamp 100.
The color wheel 103 is formed by combining fan-shaped red, green and blue color filters into a disk shape, and when rotated, it can transmit sequentially and selectively lights with wavelengths in the respective wavelength bands of red, green and blue. Light radiated from the discharge lamp 100 passes through the color wheel 103, a condensing lens 104, and a field lens 105 and is irradiated onto a liquid crystal panel 106. The color wheel 103 is rotated in synchronization with an image display by the liquid crystal panel 106, and thus optical images corresponding respectively to red, green and blue video signals are formed on the liquid crystal panel 106 on a time-division basis.
The condensing lens 104 is used to lead light transmitted through the color wheel 103 efficiently to the liquid crystal panel 106. Further, the field lens 105 is used to condense light to be transmitted through the liquid crystal panel 106 onto a projection lens 107. The optical images on the liquid crystal panel 106 are projected in a magnified state on a screen (not shown) by the projection lens 107, thereby allowing a large screen video image to be displayed in full color.
According to this system, a color image having a resolution as high as that achieved by the three-panel system can be obtained even with the use of a single liquid crystal panel. Further, this system eliminates the need to provide minute color filters in each pixel on a liquid crystal panel, and thus a yield of a liquid crystal panel is improved, thereby allowing a cost reduction of an apparatus to be achieved.
Patent Document 1: JP 2004-317528 A